PARENT SESSION
Oral Session # 81: Soil Ecology II: Microorganisms and Mycorrhizae.
Presiding: SJ Hall
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 106.

Effects of supplemental nutrients on Schizachyrium scoparium (little bluestem) with high and low AM colonization.

Antonsen, Hilde^*,1, Anderson, Roger¹, Juliano, Steven¹, ¹ Illinois State University, Normal, Illinois, United States

ABSTRACT- An experimental field study was conducted to evaluate the impacts of supplemental nutrients (N, P, K and Ca+Mg) on little bluestem grass (Schizachyrium scoparium) with a high (21.0 ± 0.7%) or low (3.2 ± 0.4%) levels of colonization by arbuscular mycorrhizal fungi (AMF). Low-colonized plants were grown in autoclaved soil in a glasshouse and transplanted into fumigated soil in the field, while high-colonized plants were started in unsterilized soil and planted into unfumigated field soil. Originally, data were analyzed by multiple univariate analysis of variance. Previous conclusions drawn from these analyses were that bases (Ca+Mg) were the limiting nutrients in this sandy prairie system. Since tools for performing multivariate statistics are now more accessible and userfriendly, a reanalysis of the data was performed. New interpretations suggest that phosphorus and bases were limited nutrients in this system, and enhanced little bluestem growth occurred when mycorrhizal colonization was low. However, none of the added nutrients had significant effects on growth for plants with high levels of colonization. This interaction is explained by the cost of having a fungal partner. Even if levels of P and Ca+Mg are high enough to sustain increased growth, available carbon sources are not sufficient for increased growth due to the drain of the fungal component. Thus, in this sandy prairie system the AMF acts as a parasitic organism.

Key words: Schizachyrium scoparium, sand prairie, arbuscular mycorrhizae, inorganic nutrients